首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   568066篇
  免费   36203篇
  国内免费   1208篇
耳鼻咽喉   7861篇
儿科学   17439篇
妇产科学   14291篇
基础医学   94321篇
口腔科学   15780篇
临床医学   49044篇
内科学   103813篇
皮肤病学   13973篇
神经病学   39997篇
特种医学   21273篇
外国民族医学   63篇
外科学   84119篇
综合类   8678篇
现状与发展   1篇
一般理论   135篇
预防医学   41594篇
眼科学   13335篇
药学   45422篇
中国医学   1622篇
肿瘤学   32716篇
  2021年   5093篇
  2019年   4667篇
  2018年   6560篇
  2017年   4838篇
  2016年   5795篇
  2015年   7023篇
  2014年   9048篇
  2013年   12957篇
  2012年   18071篇
  2011年   18965篇
  2010年   11045篇
  2009年   10097篇
  2008年   17016篇
  2007年   17710篇
  2006年   17519篇
  2005年   16633篇
  2004年   16001篇
  2003年   15030篇
  2002年   14663篇
  2001年   25200篇
  2000年   26087篇
  1999年   21300篇
  1998年   5754篇
  1997年   4935篇
  1996年   5233篇
  1995年   4779篇
  1992年   15999篇
  1991年   16583篇
  1990年   16668篇
  1989年   16030篇
  1988年   14785篇
  1987年   14637篇
  1986年   13750篇
  1985年   13129篇
  1984年   9742篇
  1983年   8343篇
  1982年   4609篇
  1979年   9485篇
  1978年   6915篇
  1977年   5802篇
  1976年   5643篇
  1975年   6442篇
  1974年   7688篇
  1973年   7172篇
  1972年   7004篇
  1971年   6719篇
  1970年   6212篇
  1969年   5904篇
  1968年   5581篇
  1967年   5029篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
A series of 1-alkyl-3,4-dihydroisoquinolines and the related 4-alkyl-1,2-dihydro-benzo[f]isoquinolines was synthesized using reactions of dialkylbenzylcarbinols and their naphthyl analogs with alkylcyanides. Experiments showed that 1-alkyl-6,7-dimethoxy-3,4-dihydroisoquinolines typically produce a hypotensive action, while the benzo-annelated structures usually exhibit a hypertensive effects. The most active compound decreases the arterial pressure in cats by 52 Torr and the effect lasts for about 4 hours. __________ Translated from Khimiko-Farmatsevticheskii Zhurnal, Vol. 40, No. 3, pp. 15–17, March, 2006.  相似文献   
92.
Extracts of the above-ground part of meadowsweet (Filipendula ulmaria L. Maxim.) demonstrate a pronounced antioxidant activity. It is established that 70% and 95% ethanol extracts contain the most active substances. Investigation of the chemical composition of the above-ground part of the plant and its 70% ethanol extract by means of qualitative reactions, thin-layer chromatography, and paper chromatography showed the presence of various phenolic compounds, including quercetin and its glycosides, dihydroquercetin, apigenin, rododendrol, esculetin, and m-hydroxybenzoic, salicylic, anisic, gallic, gentisic, ferulic, chlorogenic, and caffeic acids. __________ Translated From Khimiko-Farmatsevticheskii Zhurnal, Vol. 40, No. 12, Pp. 22–24, December, 2006.  相似文献   
93.
94.
95.
96.
97.
AIMS: To examine the effects of agents that alter potassium adenosine triphosphate (KATP) channel activity in beta-cells on cognitive function and counterregulatory hormone responses during acute hypoglycaemia, given the physiological similarities between the pancreatic beta-cell and the hypothalamic glucose-sensitive neurones (GSN) and the widespread distribution of sulphonylurea receptors in neuronal cells throughout the brain. METHODS: Ten healthy males were studied on four occasions and in random order underwent three stepped hypoglycaemic (plasma glucose aims: 3.4, 2.8, 2.4 mmol/l) and one euglycaemic (plasma glucose aim: 5 mmol/l) insulin clamps. Prior to each hypoglycaemic study, volunteers received either 10 mg glibenclamide, or 5 mg/kg diazoxide or placebo orally. Cognitive function, symptom scores and counterregulatory hormone responses were measured at each glycaemic level. RESULTS: There was no statistically significant effect of either drug on the symptoms generated or the counterregulatory hormonal response during hypoglycaemia. However, cognitive function was better preserved during hypoglycaemia in the glibenclamide-treated arm, particularly four-choice reaction time which deteriorated at a plasma glucose 2.5 mmol/l compared with 3.0 mmol/l with diazoxide (P = 0.015) and 2.9 mmol/l with placebo (P = 0.114). CONCLUSIONS: Single doses of pharmacological agents which alter membrane KATP channel activity do not affect the counterregulatory response to hypoglycaemia but may modify cognitive function during cerebral glucopenia. The unexpected effects of glibenclamide on cortical function suggest a novel action of sulphonylureas that warrants further investigation.  相似文献   
98.
Background/purpose: Vitiligo and nevus depigmentosus (ND) present similar hypopigmented macules with significantly different prognoses. Although the distinction between the two diseases is important, differential diagnosis relies on medical history and physical examination, which is far from decisive in some cases. The Mexameter® is an objective skin color-measuring device, and has been reported to provide a reproducible and sensitive means of quantifying small skin color differences. In this study, we investigated the usefulness of a Mexameter® for discriminating these diseases.
Methods: A selection of 202 hypopigmented skin lesions (182 from vitiligo and 20 from ND) were the objects of this study. Using a Mexameter, MIs were obtained from lesions and symmetrically located control skin. RMIs, ratios of the MIs of lesional skins to control skins, were calculated.
Results: The mean MIs and RMIs were significantly different for vitiligo and ND. The mean RMI of ND lesions was 74±13, which was significantly higher than that of vitiligo lesions (50±24). No ND lesion had an RMI of <50%.
Conclusion: This study shows that the Mexameter®, an objective pigment-measuring device, can be used to achieve a more accurate diagnosis of hypopigmentary disorders, and that the relative melanin index (RMI), which represents the relative pigment levels, might be a more effective parameter than the melanin index (MI) itself for comparing pigmentation differences.  相似文献   
99.
Atherosclerotic renal artery stenosis (ARAS) may cause hypertension, progressive renal failure, and recurrent pulmonary edema. It typically occurs in high risk patients with coexistent vascular disease elsewhere. Most patients with ARAS are likely to die from coronary heart disease or stroke before end-stage renal failure occurs. Recent controlled trials have shown that most patients undergoing angioplasty to treat renovascular hypertension still need antihypertensive agents 6 or 12 months after the procedure. Nevertheless, the number of antihypertensive agents required to control blood pressure adequately is lower following angioplasty than for medication alone. Trials assessing the value of revascularization for preserving renal function or preventing clinical events are only in the early recruitment phase. Revascularization should be undertaken in patients with ARAS and resistant hypertension or heart failure, and probably in those with rapidly deteriorating renal function or with an increase in plasma creatinine levels during angiotensin-converting enzyme inhibition. With or without revascularization, medical therapy using antihypertensive, hypolipidemic and antiplatelet agents is necessary in almost all cases.  相似文献   
100.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号